1. Field of the Invention
The present invention relates to a portable storage medium requiring security, such as an ID card, a pass, a prepaid card or a telephone card, and to a portable storage medium processing apparatus for performing issuance processing of the portable storage medium or collation processing at the time of operations using the portable storage medium.
2. Description of the Related Art
Recently, magnetic cards have been used in various fields as portable storage media such as telephone cards, prepaid cards and ID cards. With prevalence of such cards, however, there have been occurred problems: fraudulent processing by a third party of magnetically recorded information, e.g. fake or falsification, and illegal use of the cards.
In order to deal with the above problems, a visible image recording area may be provided on the surface of a magnetic card, and fixed visible information maybe recorded on this recording area According, security is enhanced by checking both magnetic information and visible information.
In general, however, a numerical value is employed as a visible image to be recorded as fixed information. Thus, a part of the image of the numeral value may be changed. For example, "6" may be illegally changed to "8". As has been stated above, stored magnetic information can be falsified with relative case. Thus, the security of the magnetic card becomes dependent upon the case with which the image information is falsified.
On the other hand, other methods for enhancing security have been proposed based on naked eye detection: a method using a holographic image in which an image of the user's face is directly printed on the surface of the magnetic card, or a sheet bearing the photographic image of the user's face is attached on the surface of the magnetic card (e.g. Jap. Pat. Appln. KOKAI Publication No. 3-71383), a method using precise printing techniques.
The methods using holography or precise printing, however, are expensive, and once the printed image is falsified successfully, fraudulent cards may be massproduced. In addition, in the method of attaching a thin sheet bearing the image of the user's face on the magnetic card, the sheet may be peeled off and reattached on another card illegally. Moreover, there is another method for preventing falsification of the photograph of the face, in which a mark is put on the recorded image of the face (e.g. Jap. Pat. Appln. KOKAI Publication No. 3-234670).
A generally used method of recording a visible image on a magnetic card is a thermosensitive recording method using a thermal head or a thermal transfer recording method. A recording portion on which the image is recorded by the thermosensitive recording method is formed of a thermosensitive recording material which develops color due to heat. In the thermal transfer recording method, a recording portion is formed of an ink receiving layer. In these recording portions, in general, a protection film is not provided on a recording layer.
Consequently, the fixed information recorded on the recording portion, which represents the value of the card, may be falsified by means of a pen, etc. In order to prevent falsification, it is known to form a protection film on the recording portion after the fixed information is recorded.
Even if the protection film is provided, however, the image on the recording portion can be falsified externally by means of a thermal pen, etc. in the case of the thermosensitive recording method. On the other hand, in the case of the thermal transfer recording method, a detection of falsification is easier since false information is added by ink on the protection film. However, protection film forming means, in addition to the recording means, must be provided in the card issue apparatus, resulting in complexity of the apparatus and an increase in apparatus size, processing time and costs.
There have also been proposed a non-contact recording method of recording a visible image. According to this method, a recording sheet is formed by providing, on a base sheet, a recording layer consisting of a photothermic conversion material, which absorbs a laser beam of a oscillation wavelength and converts it to heat, and a thermosensitive recording material. A laser beam modulated according to image information is radiated on the recording sheet, thereby effecting non-contact recording (e.g. Jap. Pat. Appln. KOKAI Publications Nos. 57-14096 and 2-204087).
In this recording method, however, the image forming material is the same as the thermosensitive recording material. Therefore the degree of difficulty of falsification is about the same as in the thermosensitive recording method.
As has been described above, the prior-art techniques fail to provide a sufficient check system with respect to falsification of recording portions of portable storage media, and falsification of visible images on the recording portions.